Process for production of solidified carbon dioxide and the recovery of nitrogen



Jan. 10, 1939.

DIOXIDE AND THE RECOVERY OF NITROGEN Filed Dec. 2, 1935 m 8 E 5 I I l Il I l FuRNAgE'E l I I 1 E i l l I l 5s COOLER P s:- 1'' ml! mg:

V T e MIXER 4 FILTER v 5 1 T 2 7 ml GAS STORAGE mm- 3 Q TANK nun t "i 12l I; I lull DI r Y 2 Sheets-Sheet l FUEL TANK a E g lu'nlsnxcu 13 (n if0 m T 3 ZunlSTAGE E 13 Z d o u u 3RD sum: 13 l LIQUID cu TANK HYDRATEDLIME Ix PLANT 8 [Z 03 m n. [I m E 9 a 37 a u u. E

40 Z J D. 23

l1] 0 36 5 [I 1 T u 27 Ricmvms CHAMBER J 5 13B STAGE v a Nvrnolezn CDMPRESSOR 8 LDQUID N TANK 2mm STAGE 38 mvnzleau z COMP ESSOR J D.

"3.5 m 9 x t z J 3 l E Z CONVERTER INVENTOR EA.SC1@/22idt F. A. SCHMIDT43,2 3 PROCESS FOR PRODUCTION OF SOLIDIFIED CARBON DIOXIDE AND THERECOVERY OF NITROGEN Filed DeC. 2, 1955 2 Sheets-Sheet 2 Jan. 10,1939.

4:: fligg. 2

ROTARY KILN co. FLUE GAS RESERVE co nus sAs CHAMBER 52 RTICAL COOLER 76Filter PREHEATER CARBIDE PLANT o Furn ace T FA.S 6121725664) METER Fromgas su l I Patented .Fan. 10, 193% STATES "PATENT oil-rice PROCESS FORPRODUCTION ()FSOLIDIFIED CARBON DIOXIDE AND THE RECOVERY 01F NITROGENFred a. Schmidt, South Gate, cam. Application December 2, 1935, SerialNo. 512,519

5 Claims.

vide a process to separate the carbon dioxide and m nitrogen from thegases of combustion, to solidify the carbon dioxide into "dry ice and.to recover the nitrogen for subsequent utilization.

An additional object of this invention is to provide a continuousprocess whereby lime, and flue Mi gases containing'carbon dioxide andnitrogen in large quantities, are produced by burning limestone andhydro-carbon fuels; and whereby the carbon dioxide and nitrogen areseparately recovered from the flue gases and dryice formed. 2% from thecarbon dioxide, while the nitrogen is used in a fixation plant and inparticular to produce cyanamide from carbide produced from theutilization of the lime.

These objects I accomplish by means of such 2% equipment as willfullyappear by perusal of the following specification.

In the drawings similar characters of reference indicate correspondingparts in. the several views:

Figure 1 is a diagrammatic view of the equipso ment employed in carryingout my process when a liquid hydro-carbon fuel is the source of thecarbon dioxide and nitrogen.

Figure 2 is a diagrammatic view of an additional portion of equipmentemployed when lime 36 stone and hydro-carbon fuel are the source of thecarbon dioxide and nitrogen.

Figure 3 is a diagrammatic view of a substitute portion of the equipmentemployed when natural gas, or any other hydro-carbon gas, is the source40 of the carbon dioxide and nitrogen.

Referring now to the characters'of reference on the drawings and inparticular to the equipment illustrated in Figure 1, the processcomprises the following steps: 4% Liquid hydro-carbon fuel stored intank I is pumpedto a gasifier 2 from which the gasified fuel passes to astorage tank 3. The gasifled fuel then enters a mixer l where apredetermined'proportion of air, which has been previously filtered 50and dehydrated, enters through pipe 5 and is mixed with the fuel and insuch proportion as to promote complete combustion.

After the mixture is complete, it flows through pipe 6 where it ispreheated at I to a degree slight- 55 ly below the ignition point.

(on. ea-i'zas) It then enters furnace where combustion takes placecreating flue gases containing, as usual, carbon dioxide, nitrogen,water vapor, sulphur compounds, etc. Flue gases from any source may alsobe employed in the process hereinafter described if such gases contain asufficient percentage of carbon dioxide and nitrogen.

The flue gases are then cooled to approximately 1 200 Fahrenheit in acooler 9 either by radiation or water jacketing. leaving the cooler, thegases are passed through a filter l0 where all entrained solid matteris-removed and the gases are then passedinto an automatic defrostingdehydrator H, or series of such dehydrators, where all the water vaporis condensed and drawn off the gases being reduced in the dehydrator toa temperature of to '50 Fahrenheit. The dehydrator also acts as ascrubber in that the water vapor, while condensing, unites with thesulphur compounds to form an acid which is drawn off with 20 the waterthrough valve l2.

The dehydrated and purified carbon dioxide and nitrogengases then passthrough three stages of compression, indicated generally at l3, wherethe pressure is increasedto between 2500 and 4500 pounds per square inchand which pressure varies in accordance with the temperature and densityof the mixture of gases. The gases at each stage of compression aresubjected to a cooling action by a cooler 14. As the compression of thegases takes place at the first and second stages, a certain amount ofcarbon dioxide'will be liquefied and will be drawn off into suitablestorage tanks l5 and I6 where it may b held under pressure as a liquid.From the last s age of compression the remaining carbon dioxide andgaseous nitrogen enters a converter or expanding chamber I? whereapproximately 90% of the carbon dioxide is recovered asa-snow, which isthen compressed in a snow press l8 into blocks of solidified carbon 4dioxide, commonly known as dry ice. The liquid carbon dioxide from tanksl5 and It may also be passed to the converter or may be withdrawn forother uses. 1 r

With the compressing of the snow into blocks,

the nitrogen is released and recovered at a temperature of approximately-l80 Fahrenheit.

This nitrogen is then passed, by means of pipes l9, through the coolersH of the different stages of compression and acts as the cooling medium59 therefor. The nitrogen leaves the cooler of the flrst stagecompressor. in pipe 20 and, if still at a low enough temperature, iscarried through pipe 2| into the dehydrator H where it acts as therefrigerant. If the temperature is not low pipes 22 and 23 into arefrigerator compressor 24 and after its temperature is reduced itenters pipe 25 leading to dehydrator H to be used as the refrigeranttherein.

After leaving the dehydrator ll, the nitrogen is conducted through pipe26 into a gas receiving chamber 21. The nitrogen which has beenrecovered from the snow press and used as a cooling medium in thecompressors and dehydrator is not entirely pure and contains a smallpercentage of carbon dioxide. Initial purification of the nitrogenoccurs in the gas receiving chamber 21 and is accomplishedbystratification and decanting, and the nitrogen being of less densitythan the carbon dioxide will rise to the upper portion of the chamberand may be drawn off. This Stratification is expedited by the use ofrefrigeration.

From chamber 21 the nitrogen may be allowed to flow through pipe 28 intopipe 29 into nitrogen compressors 30 where it is liquefied and thenexpanded into snow in a converter 3| and compressed into blocks ofnitrogen ice in a snow press 32. Any nitrogen which liquefies after thefirst stage of compression is drawn off into a storage tank 34 and maypass through pipe 35 into the converter 3|. Nitrogen from therefrigerator compressor 24 may also be carried through pipe 29 into thecompressors 30 and be used to form nitrogen ice.

Pure nitrogen drawn off from the upper strata in chamber 21 may beconducted through pipe may be by-passed from the 36 into pipe 31 leadingto a cyanamide plant 38 where nitrogen fixation occurs to producecyanamide, the carbide for the cyanamide plant being supplied to theplant by a conveyor 39 leading out of a carbide plant 40. The lime usedto produce the carbide is supplied by a conveyor 41! from any suitablesource and any excess quantity of lime conveYor'into a hydrated limeplant 42. The cyanamide plant, carbide plant and hydrated lime plantsare of common construction and operation.

After the pure nitrogen is drawn ofi", intermediately stratifiednitrogen containing a small percentage of carbon dioxide is passedthrough pipe 43 into a series of chemical scrubbers 44 forcompletepurification and is then released into pipe 31 from the lastscrubber.

All carbon dioxide which 'settles with some nitrogen to the bottom ofchamber 21 as a lower strata is drawn off into exhaust pipe 48 whichleads to pipe 41 and is then passed into the scrubbers where all tracesof the carbon dioxide are removed from the nitrogen.

A by-pass pipe 46. permits excess purified nitrogen to flow, if desired,from thelast scrubber into a refrigerator compressor 24 to be used forthe purposes hereinbefore described.

Also, excess purified nitrogenv may be passed directly from the lastscrubber to compressors 30 through pipes 45, 28 and 29. 1

In some instances it is desirable to conduct the nitrogen from the pipe20directly to the first scrubber 44 and to accomplish this, pipe 22extends beyond the intersection with pipe 23, as pipe 41, which leads tothe first scrubber.

In the equipment herein described, all pipes are of course suitablyvalved in order that the steps of the process may be controlled andcarried out in the manner herein stated.

I have heretofore described the lime for the carbine plant as beingsupplied from any suitable source. However, to provide a continuousenough for this purpose, it is passed throughprocess, I may provide limeand flue gas in the following manner and with the aid of the equipmentillustrated diagrammatically in Figure 2.

To accomplish this continuous process, the gaseous hydrocarbon fuelpasses through pipe 6 and is preheated at 1. From the preheater, thefuel is used to create combustion in a rotary lime kiln 49, in avertical lime kiln 50 and in a coke oven 5!. The flue gas from the twokilns and the coke oven may then be passed to cooler 9 and the processcontinued beyond the cooler as heretofore described in connection withthe equipment illustrated in Figure 1.

The main portion of the flue gas utilized will come from the rotarykiln, but due to the higher percentage of carbon dioxide in the flue gasfrom the vertical kiln, it will be used when necessary to maintain thedesired percentage of carbon dioxide in the flue gas'entering thecooler; a constant percentage of carbon dioxide being of vitalimportance in the proper operation of compressors. Additional flue gasis obtained from coke oven 5! and the flue gas from the vertical kiln 50and coke oven 5! may be held in reserve in chamber 52 and allowed topass into cooler 9 in the amount desired. Coke from the coke oven 5| aswell as the lime from the kilns is used in the production of carbide incarbide plant 40.

The main portion of lime used in carbide plant 45 is obtained from kiln49 and carried to plant 40 on a conveyor 4| while any excess lime ishydrated in the hydrated lime plant. As heretofore indicated, theprocess from the step of cooling in cooler 9 and from the step ofproducing the carbide, is the same here as in the process described inconnection with Figure 1.

From the foregoing description it will be ap parent that a continuousprocess is provided from the initial step of. burning limestone to thefinal step of forming dry ice from the separated carbon dioxide andcyanamide by fixation of the separated nitrogen and, of course, anyexcess nitrogen may be converted into nitrogen ice blocks for use as arefrigerant or may be stored as liquid nitrogen for other commercialuses.

Referring now to the equipment illustrated in Figure 3, the process isvaried in the following manner when an initially gaseous fuel, such asnatural gas, is"used to-create the combustion. The gaseous fuel passesthrough a meter 53 and is then filtered at 54 to remove any foreignsolid matter. After filtering, the gaseous fuel is dehydrated at 55 inorder to remove the water vapor and thereby permit more eificientcombustion of the fuel. Nitrogen passing through pipe 56 from pipe 25 isused as the refrigerant in the dehydrator 55. From the dehydrator thegaseous fuel passes into mixer 4 and is mixed with filtered anddehydrated air. Then the mix ture is preheated and passed to thecombustion chamber of the furnace or kiln as the case may be, and theprocess then proceeds as previously described.

The heretofore described process provides a highly efiicient means ofproducing liquid carbon dioxide, solidified carbon dioxide, liquidnitrogen, solidified nitrogen and many nitrogenous products, includingcyanamide, at a very low cost by utilizing all the products andby-products of an industry, thus providing for a large production ofuseful products at a minimum of cost.

While this specification sets forth in detail the present and preferredapplication of the process,

still in practice such deviations from such detail may be resorted to asdo not form a departure irom. the spirit of the invention as defined bythe appended claims.

Having thus described my invention, what I claim as new and'useful anddesire to secure by Letters Patent is:

l. A process for producing liquefied carbon dioxide irom gases having acarbon dioxide content, comprising the steps of cooling the gases,dehydrating the gases, compressing and subsequently cooling the gasesuntil a portion of the carbon dioxide contained therein is liquefied,

separating the liquid carbondioxide from the the remaining gases untilthe remainder ofthe carbon dioxide therein is llquefied'into anotherportion, reuniting said portions of liquid carbon dioxide, thenexpanding the reunited portions of liquid carbon dioxide into a snow andcompressing the snow, whereby the nitrogen is released.

3. A process for producing solidified carbon dioxide and gaseousnitrogen comprising the steps oi filtering and dehydrating a gaseoushydrocarbon iuel, filtering and dehydratingair, introducing the air intothe fuel in a quantity to promote combustion, causing combustion of themixture, cooling and filtering the resultant the gases after eachcompression, the compression and cooling at each stage being sufiicientto liquefy a portion of the carbon dioxide, and withdrawing that portionof the carbon dioxide which liquefies after compression and cooling ateach stage.

5. A process for producing liquefied nitrogen from gas including carbondioxide and nitrogen, the nitrogen being present in the mixture inrelatively high proportionate content, said process comprising the stepsof removing a substantial portion of the carbon dioxide content bysuccessive stages of. compression, cooling and withdrawing the liquefiedcarbon dioxide after each stage of compression, and expanding theremaining mixture in an expansion chamber after the last stage ofcompression thereby removing substantially all remaining carbon dioxidecontent in the form of snow, recovering the gaseous nitrogen from theexpansion chamber, purifying the recovered nitrogen to remove the lasttraces of carbon dioxide, and finally compressing said recovered andpurified nitrogen until substantially all of the same is liquefied.

10 to a plurality of stages of compression, cooling

